U.S. Secretary of State Mike Pompeo vowed Thursday the United States and its allies would work diplomatically to expel all Iranian troops from Syria, urging Middle East nations to forge a common stand against Tehran.

"It's time for old rivalries to end, for the sake of the greater good of the region," said Pompeo at a keynote address in Cairo.

They always anticipated U.S. support would run out, but President Donald Trump's abrupt decision to rapidly pull U.S. forces out of northeast Syria has nevertheless stunned the Kurds there, who for the past three years have been America's partner in fighting the Islamic State group.

A withdrawal will leave Syrian Kurds exposed to Turkish threats of an invasion from one side and Syrian government troops on the other.

Moscow will early next year host the leaders of Russia, Iran and Turkey to discuss the Syrian conflict, Russia's deputy foreign minister said Friday, after the United States announced it was withdrawing troops from the country.

Iran said Saturday the US presence in Syria had been "wrong and illogical" from the start, in its first official reaction to President Donald Trump's decision to withdraw troops.

"The presence of American forces was from the very start, in principle, a wrong and illogical move and a primary cause of instability and insecurity in the region," said foreign ministry spokesman Bahram Ghasemi on his Telegram channel.

Against the advice of many in his own administration, President Donald Trump is pulling U.S. troops out of Syria. Could a withdrawal from Afghanistan be far behind?

Trump has said his instinct is to quit Afghanistan as a lost cause, but more recently he's suggested a willingness to stay in search of peace with the Taliban. However, the abruptness with which he turned the page on Syria raises questions about whether combat partners like Iraq and Afghanistan should feel confident that he will not pull the plug on them, too.